Nucleic acids found in cells can be deoxyribonucleic acid or ribonucleic acid and can be genomic DNA, extrachromosomal DNA (e.g. plasmids and episomes), mitochondrial DNA, messenger RNA, miRNA, and transfer RNA. Nucleic acids can also be foreign to the host and contaminate a cell as an infectious agent, e.g. bacteria, viruses, fungi or single celled organisms and infecting multicellular organisms (parasites). Recently, detection and analysis of the presence of nucleic acids has become important for the identification of single nucleotide polymorphisms (SNPs), chromosomal rearrangements, the insertion of foreign genes, and alterations in methylation status of nucleic acids. These include infectious viruses, e.g. HIV and other retroviruses, jumping genes, e.g. transposons, and the identification of nucleic acids from recombinantly engineered organisms containing foreign genes, e.g. Roundup Ready plants.
The analysis of nucleic acids has a wide array of uses. For example, the presence of a foreign agent can be used as a medical diagnostic tool. The identification of the genetic makeup of cancerous tissues can also be used as a medical diagnostic tool, confirming that a tissue is cancerous, and determining the aggressive nature of the cancerous tissue. Chromosomal rearrangements, SNPs and abnormal variations in gene expression can be used as a medical diagnostic for particular disease states. Further, genetic information can be used to ascertain the effectiveness of particular pharmaceutical drugs, known as the field of pharmacogenomics.
Methods of extracting nucleic acids from cells are well known to those skilled in the art. A cell wall can be weakened by a variety of methods, permitting the nucleic acids to extrude from the cell and permitting its further purification and analysis. The specific method of nucleic acid extraction is dependent on the type of nucleic acid to be isolated, the type of cell, and the specific application used to analyze the nucleic acid. Many methods of isolating DNA are known to those skilled in the art, see for example the general reference Sambrook and Russell, 2001, “Molecular Cloning: A Laboratory Manual.” For example, the prior art contains examples of chemically-impregnated and dehydrated solid-substrates for the extraction and isolation of DNA from bodily fluids that employ lytic salts and detergents and which contain additional reagents for long-term storage of DNA samples e.g. U.S. Pat. No. 5,807,527 detailing FTA paper and U.S. Pat. No. 6,168,922 detailing Isocard Paper. The prior art also contains examples of particle separation methods, e.g. U.S. RE 37,891.
While many nucleic acid purification procedures are well known and have been in existence for years, these procedures can be time consuming and may employ reagents that present dangers to those performing the purification. For example, it has long been known that DNA can readily be obtained in a purified form from a test sample using organic extraction procedures, but such procedures can require several extractions and therefore can be time consuming. Additionally, the use of some organic solvents is undesirable and dangerous if proper precautions are not followed.
Accordingly, there is a need for an efficient, effective and convenient method for isolating nucleic acids from cells and preparing cell-free nucleic acids (e.g., from body fluids) for analysis.